Vibration has been used for years to promote flow in hoppers. The most direct approach is to hit the hopper with a sledge hammer. More sophisticated vibration techniques include: electromagnetic, air driven and motor drivers with eccentric weights. These vibrators applied directly to bins are sometimes effective in dislodging caked solids. Improvements have been made over the years by applying the vibrators to internal walls of the bins, or by suspending the entire hopper on elastic supports so that the vibration does not activate the entire structure. Most of the applied vibration is dissipated in unnecessary movement of the structure or of the solids stored within the hopper. This often causes structural damage and overcompaction of the bulk solids.